In electronic ignition systems, ignition coils are excited via a pickup and a control unit using switching transistors, with the coils generating the ignition voltage or ignition current. Older ignition systems with simple ignition employ a distributor to allocate the ignition voltage mechanically to the individual cylinders, whereas in modern ignition systems the cylinders are directly supplied, i.e., without mechanical distributors.
To improve the cold-starting characteristics of the engine, a high ignition energy of the ignition coil is needed for the ignition process; this generally ensures--even when the spark plug is dirty, causing a low-resistance shunt through which part of the ignition energy flows out of the ignition coil--that an ignition spark is generated between the spark plug electrodes.
As a result of this high ignition energy--which is actually not even necessary once the engine has warmed up--the useful life of the spark plugs is greatly shortened. To increase the interval between changes of the spark plugs--for example, from 20,000 kilometers to 50,000 or 100,000--improved spark plugs can be used, which however are very expensive.